1. Field of the Invention
The invention relates in general to a light emitting device and a method of manufacturing the same, and more particularly to an infrared light emitting device and a method of manufacturing the same.
2. Description of the Related Art
An infrared light emitting device is mainly applied to the optical communication industry. The current infrared light emitting device may be manufactured by a few methods, such as epitaxy, and by using a semiconductor element (III-V group element) as the material. However, the infrared light element with the middle or long wavelength must be manufactured at the low temperature, so expensive cooling equipment is needed. Alternatively, the conventional infrared light element needs to use a multi-layer film structure so that the processing complexity is increased. In addition, the ratio of the full width at half maximum (FWHM) Δλ to the peak wavelength (Peak) λ of the spectrum of the current infrared light element is not ideal.
FIG. 1A (Prior Art) is a schematic illustration showing an infrared light emitting device 1 according to the prior art. FIG. 1B (Prior Art) is a top view showing the infrared light emitting device 1 of FIG. 1A. FIG. 2 (Prior Art) shows the spectrum of the infrared light emitting device 1 of FIG. 1A. As shown in FIGS. 1A, 1B and 2, the infrared light emitting device 1 of FIG. 1A is disclosed by El-Kady et al. in “Photonics and Nanostructures-Fundamentals and Applications”, Volume 1, Issue 1, 69-77 (2003). El-Kady et al. utilize a photo process to form a photoresist layer having periodicity on a surface of a silicon substrate 10. Then, a metal layer 12 and a protection layer (e.g., a graphite layer) 14 are formed on the surface of the silicon substrate 10 by a vapor deposition process, and then a plurality of holes with a depth of 5 μm is formed on the silicon substrate 10, so as to obtain a periodic surface texture. A black body radiation source of the holes may couple photons to form a surface plasmon (SP). As shown in FIG. 2, a ratio of a FWHM (Δλ) to a peak wavelength (λ) is about 11.9%. However, such a ratio cannot satisfy the requirements in some applications. Thus, it is an important subject in the industry to develop an infrared light emitting element, which can operate at the high temperature and has the smaller ratio of the FWHM (Δλ) to the peak wavelength (λ).